* libc/include/sys/reent.h (_REENT_INIT_PTR): New macro for
initializing a struct _reent that has been dynamically allocated.
(_REENT_CHECK_MISC): New macro that checks _misc struct for
_REENT_SMALL and does nothing otherwise.
(_REENT_STRTOK_LAST): New macro for reentrant strtok.
(_REENT_MBLEN_STATE): New macro for reentrant mblen.
(_REENT_MBTOWC_STATE): New macro for reentrant mbtowc.
(_REENT_WCTOMB_STATE): New macro for reentrant wctomb.
[_REENT_SMALL](struct _misc_reent): New structure containing
miscellaneous reentrant areas needed by newlib.
[_REENT_SMALL](struct _reent): Add _misc pointer.
[_REENT_SMALL](_REENT_INIT_MISC): New macro.
* libc/string/strtok (strtok): Change to use _REENT_CHECK_MISC
and _REENT_STRTOK_LAST macros.
* libc/stdlib/mblen (mblen): Change to use _REENT_CHECK_MISC
and _REENT_MBLEN_STATE macros.
* libc/stdlib/mbtowc (mbtowc): Change to use _REENT_CHECK_MISC
and _REENT_MBTOWC_STATE macros.
* libc/stdlib/wctomb (wctomb): Change to use _REENT_CHECK_MISC
and _REENT_WCTOMB_STATE macros.